Intramedullary guidance systems and methods for installing ankle replacement prostheses

ABSTRACT

Intramedullary guidance systems and methods introduce some and/or all surgical tools and ankle prostheses components through the tibia, using minimal invasive exposure in the tibia tubercle, or retrograde through the talus, using minimal invasive exposure in planar surface of the calcaneus. The systems and methods align the talus and tibia for the installation of one or more ankle prostheses components, and also maintain that alignment during the installation using intramedullary guidance, e.g., by use of a guide pin to form an intramedullar passage along which surgical tools and prosthetic components are guided.

RELATED APPLICATIONS

This application is a divisional of co-pending U.S. patent applicationSer. No. 10/699,999, which is a divisional of U.S. patent applicationSer. No. 09/935,479 filed 23 Aug. 2001, now U.S. Pat. No. 6,673,116,which is a continuation-in-part of U.S. patent application Ser. No.09/694,100, filed Oct. 20, 2000, now U.S. Pat. No. 6,663,669, whichclaims the benefit of Provisional Patent Application No. 60/160,892,filed Oct. 22, 1999, and entitled “Ankle Replacement Systems,” all ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to ankle replacement prostheses, systems, andassociated surgical procedures.

BACKGROUND OF THE INVENTION

Until the early to mid 1970's, patients with injured or diseased anklejoints commonly resulting from osteoarthritis (age-related wear of thejoints), or rheumatoid arthritis (generalized joint inflammation causingdestructive changes), or traumatic arthritis (damage to a joint from adirect injury), had few satisfactory options when their ankle jointsfailed. Non-surgical options included weight loss, activitymodification, medication, injections, braces and therapeutic shoes. Theavailable surgical techniques included ankle arthroscopy (endoscopicexamination of the joint), ankle arthrotomy (cutting into the joint toexpose the interior) and debridement (opening the joint and removingbone spurs), osteotomy (cutting the bone to realign the joint), anklefusion (removing the joint and making it stiff), and total anklearthroplasty (removing the ankle joint and replacing it with anartificial substitute).

Many of the prior art surgical procedures were riddled with problems forthe patient. While early success was realized, there was a highlong-term term failure rate due to complications such as infection,loosening, and collapse, which lead to additional extensive surgicalprocedures.

Previous ankle replacement systems typically include a talar member,fixed to the talus, as one of their main functioning components. Thetalus, however, is relatively small, providing a small area of bone forfixation. Also, in most of these ankle replacement systems, the talarcomponent is cemented to the talus. The combination of fixation withbone cement to a small fixation area allows for erosion of the cementfrom the fixation area and an increase in compliance due to formation ofa soft tissue capsule over time. This contributes to aseptic looseningand migration of the device.

Previous ankle replacement systems are typically installed throughincisions made at or near the ankle and make use of extramedullaryalignment and guidance techniques. Such surgical procedures requiremaking large incisions at the ankle, moving the tendons and other softtissue aside, and separating the tibia and fibula from thetalus—essentially detaching the foot from the leg—to install the device.Such procedures subsequently require complicated extramedullaryrealignment and reattachment of the foot. These procedures commonlyresult in infection and extended healing time with possible replacementfailure from improper extramedullary realignment. The surgery also hasincreased risks associated with cutting or damaging neighboring nervesand tendons which may lead to further complications.

There remains a need for a total ankle replacement system that reducesthe occurrence of subsidence and aseptic loosening while retaining themajority of the foot's natural motion.

SUMMARY OF THE INVENTION

The invention provides minimally invasive intramedullary guidancesystems and methods for installing ankle prostheses. The intramedullaryguidance systems and methods make possible better long term results,because the bony cuts of the talus and tibia are properly oriented,allowing proper alignment of the total ankle prosthesis.

One aspect of the invention provides systems and methods that locate abone cutting guide in the ankle joint between a tibial bone region and atalar bone region. The systems and methods align the cutting guide in adesired orientation with the talar and tibial bone regions using anintramedullary locating element on the cutting guide that fits within anintramedullary passage formed by advancement of an intramedullary guidepin.

In one embodiment, the systems and methods enlarge the intramedullarypassage by advancing a reaming device or a drill device, e.g., over theintramedullary guide pin.

In one embodiment, the systems and methods advance a cutting instrument(e.g., a saw blade) through the cutting guide to cut either the talarbone region, or the tibial bone region, or both.

In one embodiment, a guide pin is introduced through the tibia to formthe intramedullary passage.

In one embodiment, the guide pin is introduced through a calcaneus boneregion.

The intramedullary guidance systems and methods introduce some and/orall surgical tools and ankle prostheses components through the tibia,using minimal invasive exposure in the tibia tubercle, or retrogradethrough the talus, using minimal invasive exposure in planar surface ofthe calcaneus. The systems and methods align the operative bony cuts ofthe talus and tibia for the installation of one or more ankle prosthesescomponents, and also maintain that alignment during the installationusing intramedullary guidance.

The intramedullary guidance systems and methods make possible theplacement of upper prosthetic devices anchored to the tibia, as well asthe placement of lower prosthetic devices on the talus (which may beanchored to the calcalenous, if desired), either individually or incombination. The intramedullary guidance systems and methods createsuperior cuts in the tibia and/or talus to provide near-perfectalignment with the mechanical axis of the leg, without reliance uponless-perfect extramedullary guidance. The enlarged bone surfaces supportthe fixation of larger prosthetic bases. The intramedullary guidancesystems and methods facilitate the installation of prosthesis systemsthat provide greater stability and stress absorption for the prostheticankle joint, and decrease the probability of prosthesis loosening andsubsidence.

The talar prosthetic component may include with a stem that extends intothe calcaneus. This allows for an increased amount of bone to helpsupport the talar component, although reduced motion of the subtalarjoint may result.

In addition, the fixation of the tibial prosthetic component may beimproved when combined with intramedullary placement of a tibial stem,which attaches to the tibial plafond.

Other objects, advantages, and embodiments of the invention are setforth in part in the description which follows, and in part, will beobvious from this description, or may be learned from the practice ofthe invention.

DESCRIPTION OF THE DRAWINGS

FIG. 1. is a view of the lower leg and foot skeleton.

FIG. 2 is a lateral view of a human foot and lower leg skeleton with thefibula shown in an assembly format and having a planarly resected tibiaand talus.

FIG. 2 a is a posterior view of a human foot and lower leg skeleton withthe fibula not shown and planar cuts of the tibia and talus aredepicted.

FIG. 3 shows an intramedullary guidance system for providingintramedullary alignment of the tibial and/or talar cuts, one end of thesystem being oriented toward the tibia and the other end oriented towardthe talus.

FIG. 4 is a lateral view of a lower leg and foot demonstrating theintramedullary insertion of a guide pin through the superior part of thetibia and terminating in the talus.

FIG. 5 is a lateral view of a lower leg and foot demonstrating theintramedullary insertion of a guide pin through the plantar surface ofthe calcaneus, passing through the talus and terminating in the tibia atvariable lengths.

FIG. 5 a is a sectional view of a foot and depicts the insertion andremoval of a guide pin through the plantar surface of the calcaneus,passing through the talus and terminating in the tibia, to produce anintramedullary channel, which may be made of various dimensions by usingthe guide pin to also direct the course of intramedullary reamers.

FIG. 6 is a lateral sectional view of the lower leg and foot showing theguide pin surrounded by the reaming instrument creating theintramedullary passage.

FIG. 7 is a lateral view and partial cross section of the human lowerleg and foot showing the intramedullary channel and a resected portionof the anterior lower tibia to allow easier insertion of anintramedullary cutting guide.

FIG. 8 is a posterior section of the lower leg and foot with the fibulanot shown and depicting the insertion of the intramedullary cuttingguide between the tibia and the talus.

FIG. 9 is a perspective view of a talo-calcaneal reaming jig.

FIG. 9 a is a lateral/partial sectional view depicting the insertion ofthe reaming tool in the talo-calcaneal reaming jig for the posteriorlydirected inferior stem to help support the talar component (the drillhole and stem can be only in the talus or extend into the calcaneus forincreased stability, and the anterior-posterior position of the talarsupport stem can be variable).

FIG. 9 b is a cross-sectional view of the talo-calcaneal jig and channelas positioned on the talus.

FIG. 9 c is a sectional view of resultant channel after the jig isremoved, also showing the talar support stem.

FIG. 10 is a lateral cross-sectional view of the upper prosthetic body,showing the tibial stem and tibial component.

FIG. 10 a is a side view of an alternative embodiment of an upperprosthetic body with a shorter tibial stem than shown in FIG. 10.

FIG. 11 shows the insertion of a tibial stem through the calcaneus andtalus, and (if needed) through an anti-rotational sleeve.

FIG. 12 is a perspective view of the optional anti-rotational sleeve forthe tibial stem.

FIG. 13 is a lateral cross sectional view of the tibial stem in thelower tibia and fixed with screws and (optionally) with theanti-rotational sleeve.

FIG. 14 shows a lateral cross sectional view of a lower prosthetic bodyin the foot, including the talar component with posterior fixation blade(if needed), talar fixation stem (extending into the calcaneus), andanterior talo-calcaneal fixation screws.

FIG. 15 shows both the upper and lower prosthetic bodies.

FIG. 16 shows an alternative lower prosthetic unit, with talar fixationstem at various angles.

FIG. 17 shows another alternative lower prosthetic unit, with talarfixation stem at various angles.

DESCRIPTION OF THE INVENTION

I. Anatomy of the Ankle

Referring to FIG. 1, the foot comprises fourteen phalanges or toe bones11 connected to the metatarsus bones 13. There are also seven tarsalbones 14, of which the talus 15 supports the tibia 16 and the fibula 18,and the heel bone or calcaneus 17. Of the tarsal bones, the talus 15 andthe calcaneus 17 are the largest and are adjacent to each other. Theother tarsal bones include the navicular 19, three cuneiforms 21, andthe cuboid 23.

II. Intramedullary Guidance System

In performing a total ankle replacement procedure, it is desirable tocut away bone on the inferior end of the tibia 16 and/or the superiorend of the talus 15, to thereby form a planar surface or surfaces 25, asFIG. 2 and FIG. 2 a shows (in FIG. 2 a, the tibia 16 and talus 15 havebeen resected with the removed portions shown in phantom lines, leavingtwo planar surfaces 25).

A planar surface increases the amount of bone available for the fixationof a selected prosthetic base. This provides greater stability and lessstress absorption. This also decreases the probability of prosthesisloosening and subsidence.

FIG. 3 shows the components of an intramedullary guidance system 10 forproviding a desired alignment of the tibia and talar before and whilethe tibial and/or talar cuts shown in FIG. 2 are made.

As shown in FIG. 3, the system 10 includes an intramedullary guide pin27. The intramedullary guide pin 27 is made, e.g., of an inert materialused in the surgical arts, such as surgical steel. The guide pin 27 maypossess a range of desired diameters 29, depending upon the function orfunctions it is intended to perform.

For example, the diameter 29 may be relatively small, e.g., about 2 mmto 4 mm, if the pin 27 is to be used principally to form anintramedullary void, as will be described later. The diameter 29 can bemade larger, e.g., upwards to about 10 mm, if the pin 27 is to be usedto guide passage of a surgical instrument, such as an intramedullaryreamer or drill, to form an enlarged intramedullary void, as will alsobe described later.

In use, the guide pin 27 may be introduced through the tibia (as FIG. 4shows) or through the calcaneus (as FIG. 5 shows). Before the guide pin27 is introduced, the foot and ankle are first aligned in an acceptableposition. One skilled in the art will recognize that this may requiresurgically opening the ankle joint to loosen contractures (permanentcontraction of muscles, ligaments, tendons) and scarring.

When introduced through the tibia (see FIG. 4), a minimal exposure 200is made at the tibial tubercle with an awl. Once the exposure has beenmade, the exposure may be kept open under distraction, pulling of theskin, or any other method common in the surgical arts. Non invasivevisualization of the procedure can be accomplished through fluoroscopyor real time MRI, as well as through other means well known to thoseskilled in the art. Alternatively, or in conjunction with such lessinvasive means of visualization, open visualization may be used for partand/or all of the procedure.

In this approach, the guide pin 27 passed through the tibia 16, thetibial plafond, and enters the talus.

When introduced through the calcaneus (see FIG. 5), the guide pin 27 isplaced retrograde through a minimal exposure in the calcaneus 17. Theexposure may be kept open under any method common in the surgical artsand previously discussed. As with the tibial approach, non invasivevisualization of the calcaneus approach can be accomplished throughfluoroscopy or real time MRI, as well as through other means well knownto those skilled in the art. Alternatively, or in conjunction with suchless invasive means of visualization, open visualization may be used forpart and/or all of the procedure.

In this approach, the guide pin 27 passes through the calcaneus, throughthe talus 15, through the tibial plafond, and into the tibial shaft.

As FIG. 5 a shows, upon removal, the guide pin 27 leaves behind anintramedullary guide void or passage 28 through the region where thetibia adjoins the talus. The passage 28 is sized according to thediameter 29 of the guide pin 27, or with a reamer to an appropriate sizeconsistent with the size of the bones (the calcaneus, the talus, and thetibia).

As FIG. 7 shows, once the passage 28 is formed, an anterior section S ofthe tibia 16 can be removed by cutting, to expose the anterior portionof the ankle joint and the guide passage 28.

As shown in FIG. 3, the system 10 also includes an intramedullarycutting guide 31, which is introduced into the ankle through an anteriorsurgical approach. In use, the intradmedullary cutting guide 31functions to guide the saw blade used to create the planar surfaces 25on the tibia and/or talus, as shown in FIG. 2. For this purpose, thecutting guide includes one or more cutting slots 33, through which thesaw blade passes. As shown in FIG. 3, the cutting guide 31 also includesan intramedullary locating feature, which in the illustrated embodimenttakes the form of an intramedullary locating post 35 (see FIG. 3).

In use (see FIG. 8), the intramedullary cutting guide 31 may be insertedanteriorly into the ankle joint after the resection of a small amount ofbone from the anterior “lip” of the tibia. The alignment post 35 fitsinto the intramedullary guide passage 28 in both the talus and tibia.The intramedullary post 35 aligns the cutting guide 31 in the desiredorientation with the talus 15 and tibia 16. Intramedullary guidanceenables the surgeon to produce bony cuts that more closely approximatethe mechanical axis of the leg, which extramedullary guides cannot do.

Oriented by the intramedullary post 35, the upper slot 33 of the cuttingguide 31 is aligned with the tibial shaft. The lower slot 33 is alignedin the same direction into the dome of the talus. The intramedullarypost 35 maintains alignment as a bone saw is passed through the slots33, across the end regions of talus and tibia. The aligned planarsurfaces 25 are thereby formed with intramedullary guidance. Removal ofthe cutting guide 31 exposes these planar surfaces 25, as FIG. 2 andFIG. 2 a show. With intradmedullary guidance, the cuts are superior tocuts using extramedullary guidance. Extramedullary guidance systems relyon surface bony prominences and visualization of the anterior anklejoint. These landmarks are inconsistent and can misdirect bony cuts bythe surgeon.

The intramedullary guidance system 10 can be conveniently used withvarious surgical instruments or prosthetic parts. Because extramedullaryalignment is avoided, more precise alignment can be made.

For example, as shown in FIG. 6, prior to removal of the guide pin 27and the use of the cutting guide 31 to form the tibial and talar cuts,the guide pin 27 can serve an additional function, namely, to guide thepassage of an intramedullary reaming device or a cannulated drill 30. Inthis arrangement, the guide pin 27 is used to direct the reaming device30 over it. A minimally larger exposure will be required on the bottomof the foot to allow the passage of the reaming device or drill bit overthe guide pin 27.

Depending upon the manner in which the guide pin 27 is inserted, thereaming device 30 can be guided by the intramedullary guide pin 27,either along a superior path, through the tibia and into the talus (asFIG. 4 shows), or along an inferior path, through the calcaneus andtalus and into the tibia (as FIG. 5 shows). Guided by the pin 27, thereaming device 30 leaves behind an enlarged intramedullary void orpassage 28.

Alternatively, the guide pin 27 and reaming device 30 may be placedthrough the tibia or calcaneus simultaneously, or a reaming rod may beplaced through the tibia or calcaneus without a guide pin 27, althoughit is preferable to use a guide pin. The reamer device 30 is preferably5, 6, 7, 8, 9, or 10 mm wide, depending on the size of the patient'stibia 16.

In this arrangement, the alignment post 35 of the cutting guide 31 issized to fit into the enlarged reamed intramedullary passage 28. Asbefore described, the post 35 aligns the cutting guide 31 in the desiredorientation with the talus and tibia for forming the end cuts, as wellmaintain the alignment of the reamed intramedullary passage 28.

The size of the alignment post 35 of the cutting guide 31 depends uponhow the intramedulary channel is formed. For example, if just a guidepin is used to form the channel, the post 35 will be sized smaller thanif an intramedullary reamer is used in forming the channel. If just theguide pin is used to form the channel, straightforward, minimallyinvasive percutaneous access can be used to insert the guide pin intothe calcaneus, into the talus and tibia, thereby forming the relativelysmall diameter intradmedullary channel.

An upper prosthesis body may be fixed directly to planar cut of thetibia with or without a tibial stem. A lower prosthesis body of thetalus may likewise be fixed directly to the planar cut of the talus, orwith a fixation stem into the talus or into both the talus and thecalcaneus. The upper and lower prosthesis bodies may be used incombination or singly. As will now be described in greater detail later,stemmed upper or lower prostheses may be located on the planar cuts,either individually or in combination.

III. Stemmed Upper Prosthetic Device

The reamed intramedullary passage 28 formed in the tibia using theintramedullary guidance system 10 can, e.g., serve to accept a stemmedupper prosthetic body 170, as FIG. 10 shows. The stemmed upperprosthetic body can take various forms. Certain representativeembodiments are found in U.S. patent application Ser. No. 09/694,100,now U.S. Pat. No. 6,663,669, filed Oct. 20, 2000, entitled “AnkleReplacement System,” which is incorporated herein by reference.

In one embodiment (FIG. 10), the upper prosthetic body 170 comprises anelongated tibial stem 150. The tibial stem 150 may be made of any totaljoint material or materials commonly used in the prosthetic arts,including, but not limited to, metals, ceramics, titanium, titaniumalloys, tantalum, chrome cobalt, surgical steel, or any other totaljoint replacement metal and/or ceramic, bony in-growth surface, sinteredglass, artificial bone, any uncemented metal or ceramic surface, or acombination thereof. The tibial stem 150 may further be covered with oneor more coatings such as antimicrobial, antithrombotic, andosteoinductive agents, or a combination thereof. These agents mayfurther be carried in a biodegradable carrier material with which thepores of tibial stem 150 may be impregnated. See U.S. Pat. No.5,947,893.

The tibial stem 150 may be variable lengths, e.g., from 2 cm to 30 cmand variable widths, e.g., from 6 to 12 mm. In the preferred embodiment,the tibial stem 150 is preferably approximately 6 inches in length. Ofcourse, it should be understood that the disclosed tibial stem could beof virtually any length, depending upon the size of the patient, his orher bone dimensions, and the anticipated future mobility of the patient.For example, as FIG. 10 a shows, the upper prosthetic body 170′ cancomprises a shorter tibial stem 150′ having a diameter generally thesame size (or slightly larger) than the guide pin that forms the passage28. The body 170′ can also include several short, spaced apartderotation pegs 171.

The tibial stem 150 may be inserted into the reamed intramedullarypassage 28 either superiorly (through the tibia), or inferiorly (throughthe calcaneus and talus and into the tibia), depending upon the pathalong which the guide pin 27 and reaming device 30 have followed.

For example, as depicted in FIG. 4, when the passage 28 is made by thepin 27 and reaming device 30 superiorly though the tibia, the tibialstem 150 is inserted in a superior path through the tibia. Alternately,as depicted in FIGS. 11 to 13, when the passage 28 is made by the pin 27and reaming device 30 retrograde through the calcaneus, the tibial stem150 may be introduced inferiorly through the retrograde passage 28through the calcaneus and talus into the tibia (FIG. 11).

The stem 150 is fixed in the lower tibia (FIG. 13). The tibial stem 150may be fixed in the tibia 16 with poly(methylmethacrylate) bone cement,hydroxyapatite, a ground bone composition, screws, or a combinationthereof, or any other fixation materials common to one of skill in theart of prosthetic surgery. An anti-rotational sleeve 406 (see FIG. 12)can also be used alone or in combination with other fixation devices.

In a preferred embodiment, the tibial stem 150 is fixed to the tibia 16with screws 125 a and 125 b. If screws are used, they can extendanteriorly, posteriorly, medially, laterally and/or at oblique angles,or any combination thereof.

Optionally, a sleeve 406 (see FIGS. 11 and 12) may be placed about thestem 150, e.g., as the stem is passed between the talus and tibia. Thesleeve 406 engages bone along the passage 28. The sleeve 406 imparts ananti-rotational feature, including, e.g., outwardly extending fins. Thesleeve 406 may be used in combination with the screws or alone withoutthe screws.

The distal end of the tibial stem 150 may additionally have interlockingcomponents, common to those of skill in the art, at its lower surface toallow other components of the upper prosthesis body to lock into thetibial stem. In a preferred embodiment, the tibial stem 150 has a MorseTaper 115 b at its lower surface to which a concave dome 155 isattached. The dome 155 can be made of a plastic, ceramic, or metal. Thedome 115 articulates with the lower ankle joint surface, which can bethe talus bone itself or a lower prosthetic body fixed to the talus, aswill now be described.

IV. Stemmed Lower Prosthesis Body

A lower prosthetic body can be supported on the talus, either alone orin association with an upper prosthetic body mounted in the tibia. Theupper prosethetic body may be stemmed, as just described, or affixeddirectly to the tibia without use of a stem. Likewise, the lowerprosthetic body may be stemmed or affixed directed to the talus. Certainrepresentative embodiments are found in U.S. patent application Ser. No.09/694,100, now U.S. Pat. No. 6,663,669, filed Oct. 20, 2000, entitled“Ankle Replacement System,” which is incorporated herein by reference.

In one embodiment, the stem for the talar component does not extendbeyond the inferior surface of the talar. In another embodiment, asubtalar joint (i.e., the joint formed between talus and calcaneus) isfused to allow fixation of the lower prosthesis body to both the talusand calcaneus. The subtalar joint may be fused using any method commonto those of skill in the surgical arts including, but not limited to,fusion with, for example, poly(methylmethacrylate) bone cement,hydroxyapatite, ground bone and marrow composition, plates, and screws,or a combination thereof.

FIG. 14 shows one method of fusing the talus 15 to the calcaneus 17using a stem 110, a plate 130, and screws 133 a, 133 b. Thetalo-calcaneal stem 110 is shown with a Morse Taper 115 a protrudingfrom the stem 110 and extending beyond the proximal (top) surface of thetalus 15. In another embodiment, the Morse Taper could extend down fromthe talar component into the stem. FIG. 14 also shows an arrangement inwhich the lower end of the tibia has not been cut and does not carry aprosthesis.

The talo-calcaneal stem 110 may be made of various materials commonlyused in the prosthetic arts including, but not limited to, titanium,titanium alloys, tantalum, chrome cobalt, surgical steel, or any othertotal joint replacement metal and/or ceramic, bony in-growth surface,sintered glass, artificial bone, any uncemented metal or ceramicsurface, or a combination thereof. The talo-calcaneal stem 110 mayfurther be covered with various coatings such as antimicrobial,antithrombotic, and osteoinductive agents, or a combination thereof.These agents may further be carried in a biodegradable carrier materialwith which the pores of the surface of the talo-calcaneal stem 110 maybe impregnated. See U.S. Pat. No. 5,947,893, which is incorporatedherein by reference. If desired, the talo-calcaneal stem may be coatedand/or formed from a material allowing bony in-growth, such as a porousmesh, hydroxyapetite, or other porous surface.

The talo-calcaneal stem 110 may be any size or shape deemed appropriateto fuse the subtalar joint of a patient and is desirably selected by thephysician taking into account the morphology and geometry of the site tobe treated. For example, the stem 110 may be of variable lengths, from 2cm to 12 cm, and variable widths, from 4 to 14 mm. In a preferredembodiment, the talo-calcaneal stem 110 is approximately 65 to 75 mm inlength and approximately 7 to 10 mm wide. While in the disclosedembodiment the stem 110 has a circular cross-section, it should beunderstood that the stem could formed in various other cross-sectionalgeometries, including, but not limited to, elliptical, polygonal,irregular, or some combination thereof. In addition, the stem could bearced to reduce and/or prevent rotation, and could be of constant orvarying cross-sectional widths.

The physician is desirably able to select the desired size and/or shapebased upon prior analysis of the morphology of the target bone(s) using,for example, plain film x-ray, fluoroscopic x-ray, or MRI or CTscanning. The size and/or shape is selected to optimize support and/orbonding of the stem to the surrounding bone(s).

As FIGS. 9 a to 9 c show, the talo-calcaneal stem 110 can be passed fromthe top of the talus 15 into the distal calcaneus 17 through a cavity601 that is drilled through the talus 15 and calcaneus 17. The cavity601 is preferably drilled after the surface of the talus 15 has cut andflattened, and after the location of the upper prosthesis body.

A suitable jig 600 (see FIG. 9) may be placed in the joint to assistwith locating and placing the cavity 601. Certain representativeembodiments are found in U.S. patent application Ser. No. 09/694,100,now U.S. Pat. No. 6,663,669, filed Oct. 20, 2000, entitled “AnkleReplacement System,” which is incorporated herein by reference. The jig600 includes a drill guide 620 and a post 610 that, in use, rests in theintramedullary passage 28 (see FIGS. 9 a and 9 b). The drill guide 620can extend from posterior to anterior (as FIG. 9 shows), oralternatively, from anterior to posterior.

The drill bit 603 for the jig 600 (see FIG. 9 a) is preferably about ½mm wider than the width of the talo-calcaneal stem 110. Thetalo-calcaneal stem 110 may be further adapted so that thetalo-calcaneal stem 110 is inserted as the cavity is being drilled or sothat the talo-calcaneal stem itself is used to drill the hole.

Once the cavity 601 is formed, any easily accessed cartilage from thetalo-calcaneal joint may be scraped, e.g., using a small angled curet orany other instrument commonly used in the surgical arts. The subtalarjoint can then be fused by passing a talo-calcaneal stem 110 down thecavity 601. The cavity 601 may be partially filled with a bone cementprior to the installation of the talo-calcaneal stem 110 to help fix thetalo-calcaneal stem 110 to the subtalar joint. Desirably, the stem 110incorporates screw holes or other openings to accommodate interlockinghardware, such as screws, to increase fixation and minimize rotation.

The stem 110 desirably includes a Morse Taper 115 a. A cap 160 a fits onthe Morse Taper 115 a to form an articulating joint surface with theupper prosthesis. The upper surface of the cap 160 can be designed tofit the particular needs and walking requirements anticipated by thephysician and patient. For example, a low demand surface, such as for anindividual of advanced years having a less-active lifestyle, couldcomprise a simple smooth arc, without the “peaks and valleys” of thetalus 15 that run from anterior to posterior. In addition, a low demandsurface may not require a difference in the anterior to posterior talarwidth, which in an adult male can be approximately 4 to 5 mm wider inits anterior portion than its posterior portion. A higher demandsurface, for a more active individual, may incorporate the trochlea(valley) in the talus as well as various other anatomical features foundon the talus.

Desirably, as best seen in FIG. 16, the stem 110 a extends downward fromthe cap 160 a, forming an angle α relative to the vertical axis—takenrelative to the longitudinal axis of cap 160 a (front to rear of thefoot). In one embodiment, the angle α will range from 105° to 205°,depending upon the size and orientation of the calcaneus 17 as well asthe position of the lower prosthesis body. Moreover, as best seen inFIG. 17, the stem may form an angle β relative to the verticalaxis—taken relative to the transverse axis of the cap 160 b (medial tolateral side of the foot). In a preferred embodiment, the angle β willrange from 155° (on the medial side of the foot) to 240° (on the lateralside of the foot), depending upon the size and orientation of thecalcaneus 17 as well as the position of the lower prosthesis body.Desirably, the lower portion of the stem of the implant will not extendoutside of the calcaneus.

As shown in FIG. 14, a plate 130 may be fixed to the top of the talus15. The plate 130 can have an overhang portion 131 which allows theplate 130 to overlap both the talus 15 and part of the calcaneus 17. Theplate 130 and overhang portion 131 may be made of various materialscommonly used in the prosthetic arts including, but not limited to,polyethylene, biologic type polymers, hydroxyapetite, rubber, titanium,titanium alloys, tantalum, chrome cobalt, surgical steel, or any othertotal joint replacement metal and/or ceramic, bony in-growth surface,sintered glass, artificial bone, any porous metal coat, metal meshes andtrabeculations, metal screens, uncemented metal or ceramic surface,other biocompatible materials, or any combination thereof. The plate 130and overhang portion 131 may further be covered with various coatingssuch as antimicrobial, antithrombogenic, and osteoinductive agents, or acombination thereof. See U.S. Pat. No. 5,866,113 to Hendriks, et al,incorporated herein by reference. These agents may further be carried ina biodegradable carrier material with which the pores of the plate 130and overhang portion 131 may be impregnated. In one preferredembodiment, the tray comprises a metal-backed polyethylene component.

The plate 130 and/or the overhang portion 131 may be fixed to thesubtalar joint 90 with poly(methylmethacrylate) bone cement,hydroxyapatite, a ground bone and marrow composition, screws, or acombination thereof, or any other fixation materials common to one ofskill in the art of joint replacement surgery. In a preferredembodiment, the plate 130 and overhang portion 131 are fitted over theMorse Taper 115 a of the talo-calcaneal stem 110 and fixed to the talus15 and calcaneus 17 with screws 133 a and 133 b. In another embodiment,the posterior overhang portion 131 can be eliminated.

The lower prosthesis body may be formed in a single unit or, asillustrated, as a multi-component prosthesis.

In other embodiments, the upper prosthesis body may additionallycomprise a fibular prosthesis of any variety known in the art of jointreplacement. The fibular prosthesis would replace the inferior end ofthe fibula, especially when this prosthesis is used to revise a totalankle replacement system that has removed the distal end of the fibula.In still further embodiments, either the lower prosthesis body, upperprosthesis body, or both, as described above, may be fixed intostrengthened or fortified bone. The bones of the subtalar joint, tibia,or fibula may be strengthened prior to or during fixation of theprosthesis using the methods described in U.S. Pat. No. 5,827,289 toReiley. This type of bone strengthening procedure is particularlysuggested for osteoporotic patients who wish to have a total anklereplacement.

It should be appreciated that installed prosthetic system need notinclude a calcaneal stem. Thus, the system would only include the tibialstem, the tibial component and the talar component. In this case therewould be not Morse Taper holes or stems on the under surface of thetalar component, just a flat or minimally stem component with or withoutscrew holes for screw fixation.

Likewise, the installed prosthetic system need not include a tibial stemcomponent. In this case, the system would include the tibial componentwithout the Morse Taper attachments on its superior surface, the talarcomponent, and the calcaneal stem component.

Furthermore, the installed prosthetic system need not include anystemmed component being utilized. However, the intramedullary guidancesystem 10, deployed either superiorly from the tibia, or inferiorly fromthe calcaneus, would still provide intramedullary alignment of thetibial and talar cuts. In this arrangement, the tibial component and thetalar component would be utilized, without Morse Taper stems or holes oneither implant, but the intramedullary guidance system would still beused to insure properly aligned cuts in the talus and tibia.

It should be understood that the devices and methods of the presentinvention could be used as an index (initial) total ankle replacement,as well as a revision ankle replacement. If used as a revision device,only a portion of the disclosed methods and devices may be necessary inconjunction with such a procedure.

Other embodiments and uses of the inventions described herein will beapparent to those skilled in the art from consideration of thespecification and practice of the inventions disclosed. All documentsreferenced herein are specifically and entirely incorporated byreference. The specification should be considered exemplary only withthe true scope and spirit of the invention indicated by the followingclaims. As will be easily understood by those of ordinary skill in theart, variations and modifications of each of the disclosed embodimentscan be easily made within the scope of this invention as defined by thefollowing claims.

1. A method of installing an ankle prosthesis system comprising makingan intramedullary passage into the tibial shaft retrograde through thecalcaneus, passing a tibial stem component inferiorly through theintramedullary passage into the tibial shaft, fixing the tibial stemwithin the tibial shaft, and coupling an artificial tibial joint surfaceto the tibial stem component,
 2. A method as in claim 1 wherein thepassage is made by a guide pin.
 3. A method as in claim 1 wherein thepassage is made by a reamer.
 4. A method as in claim 1 wherein thetibial stem is adapted to receive at least one fixation screw to fix thetibial stem within the tibial shaft.
 5. A method as in claim 1 whereinthe tibial stem is fixed within the tibial shaft with bone cement.
 6. Amethod as in claim 1 wherein the tibial stem is fixed within the tibialshaft with hydroxyapatite.
 7. A method as in claim 1 wherein the tibialstem is fixed within the tibial shaft with a ground bone composition. 8.A method as in claim 1 wherein the tibial stem includes ananti-rotational element.
 9. A method as in claim 1, further comprisingfixing an artificial talar joint surface to the talus.
 10. A method asin claim 1, further comprising forming a cavity in the talus, passing atalar stem through the cavity, fixing the talar stem within the talus,and coupling an artificial talar joint surface to the talar stem.
 11. Amethod as in claim 1, further comprising forming a cavity in the talusand calcaneous, passing a talar-calcaneal stem through the cavity acrossthe talar-calcaneal joint, fixing the talar stem within the cavity tofuse the talar-calcaneal joint, and coupling an artificial talar jointsurface to the talar-calcaneal stem.
 12. A method as in claim 1 whereinthe artificial tibial joint surface is of convex configuration.
 13. Aprosthesis system comprising a tibial stem sized and configured forinferior passage into the tibial shaft through an intramedullary passageformed retrograde through the calcaneus into the tibial shaft, and anartificial tibial joint surface sized and arranged to be coupled to thetibial stem.
 14. A prosthesis system as in claim 13 wherein theartificial tibial joint surface is of convex configuration.
 15. Aprosthesis system as in claim 13, further comprising an artificial talarjoint surface adapted to be fixed to the talus and for articulation withthe artificial tibial joint surface.
 16. A prosthesis system as in claim15 wherein the artificial talar joint surface is of concaveconfiguration.
 17. A prosthesis system as in claim 15, furthercomprising a talar stem sized and arranged for fixation within the talusand to be coupled to the artificial talar joint surface.